Methods of etching silicon-oxide-containing compositions

ABSTRACT

The invention encompasses a method of enhancing selectivity of etching silicon dioxide relative to one or more organic substances. A material comprising one or more elements selected from Group VIII of the periodic table is provided within a reaction chamber; and a substrate is provided within the reaction chamber. The substrate has both a silicon-oxide-containing composition and at least one organic substance thereover. The silicon-oxide-containing composition is plasma etched within the reaction chamber. The plasma etching of the silicon-oxide-containing composition has increased selectivity for the silicon oxide of the composition relative to the at least one organic substance than would plasma etching conducted without the material in the chamber. The invention also encompasses a plasma reaction chamber assembly. The assembly comprises at least one interior wall, and at least one liner along the at least one interior wall. The liner comprises one or more of Ru, Fe, Co, Ni, Rh, Pd, Os, W, Ir, Pt and Ti.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patent application Ser. No. 09/652,530, which was filed on Aug. 31, 2000, now U.S. Pat. No. 6,547,979.

TECHNICAL FIELD

The invention pertains to methods of enhancing selectivity of silicon dioxide relative to one or more organic materials, and further pertains to reaction chamber configurations.

BACKGROUND OF THE INVENTION

Semiconductor processing frequently involves etching of silicon-oxide-containing materials, such as, for example, silicon dioxide, borophosphosilicate glass (BPSG), etc. Semiconductor processing also frequently involves patterning etched materials with organic photoresist masking materials. Organic photoresist materials can be either positive or negative photoresists, and can include, for example, novolac and cyclized synthetic rubber resin. A difficulty which can occur in etching silicon-oxide-containing materials results from limited selectivity of present etch methods for silicon-oxide-containing materials relative to organic masking materials. Such difficulty is described with reference to FIGS. 1–3.

Referring first to FIG. 1, a semiconductor wafer fragment 10 is illustrated. Wafer fragment 10 comprises a substrate 12 having a silicon-oxide-containing layer 14 thereover. Substrate 12 can comprise, for example, monocrystalline silicon lightly-doped with a p-type background dopant. To aid in interpretation of the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.

Layer 14 can comprise, for example, silicon dioxide; can consist essentially of silicon dioxide, or can consist of silicon dioxide. Also layer 14 can comprise a doped silicon oxide, such as, for example, BPSG.

A patterned masking layer 16 is shown formed over silicon-oxide-containing layer 14. Masking layer 16 can comprise, for example, an organic photoresist material, and can be patterned by photolithographic processing.

Referring to FIG. 2, wafer fragment 10 is subjected to etching conditions which etch into silicon-oxide-containing material 14 to form an opening 18 extending therein. A suitable etch for silicon-oxide-containing material 14 is a plasma etch utilizing one or more of CF₄, C₂F₆, H₂, C₃F₈, and CHF₃. FIG. 2 shows a thickness of masking layer 16 reduced during the etching of oxide layer 14. Such reduction in thickness occurs due to non-selectivity of the etch conditions for oxide material 14 relative to masking material 16. Generally, the etching conditions will have some selectivity for oxide layer 14, in that the material of oxide layer 14 will etch faster than will the material of organic masking layer 16. However, the selectivity is not absolute, and accordingly some of the organic material of layer 16 etches during the etching of the silicon oxide of layer 14.

Referring to FIG. 3, wafer fragment 10 is shown after continued etching of layer 14. Such continued etching has removed layer 16 (FIG. 2) from over layer 14. Such removal of layer 16 can be problematic in further processing steps.

It would be desirable to develop alternative methods for etching silicon-oxide-containing materials with enhanced selectivity for the silicon-oxide-containing materials relative to organic materials.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a method of enhancing selectivity of etching silicon dioxide relative to one or more organic substances. A material comprising one or more elements selected from Group VIII of the periodic table is provided within a reaction chamber; and a substrate is provided within the reaction chamber. The substrate has both a silicon-oxide-containing composition and at least one organic substance thereover. The silicon-oxide-containing composition is plasma etched within the reaction chamber. The plasma etching of the silicon-oxide-containing composition has increased selectivity for the silicon oxide of the composition relative to the at least one organic substance than would plasma etching conducted without the material in the chamber.

In another aspect, the invention encompasses a plasma reaction chamber assembly. The assembly comprises at least one interior wall, and at least one liner along the at least one interior wall. The liner comprises one or more of Ru, Fe, Co, Ni, Rh, Pd, Os, W, Ir, Pt and Ti.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below with reference to the following accompanying drawings.

FIG. 1 is a diagrammatic, fragmentary, cross-sectional view of a semiconductor wafer at a preliminary processing step of a prior art method.

FIG. 2 is a view of the FIG. 1 wafer fragment shown at a prior art processing step subsequent to that of FIG. 1.

FIG. 3 is a view of the FIG. 1 wafer fragment shown at a prior art processing step subsequent to that of FIG. 2.

FIG. 4 is a flow chart diagram of a first embodiment method of the present invention.

FIG. 5 is a flow chart diagram of a second embodiment method of the present invention.

FIG. 6 is a diagrammatic, cross-sectional view of a reaction chamber apparatus which can be utilized in methodology of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).

The invention encompasses methods for increasing selectivity of silicon oxide etching relative to organic materials. One embodiment of the present invention is described with reference to FIG. 4. At an initial step 100 a material comprising one or more elements from Group VIII of the periodic table (i.e., one or more of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt) is provided within a reaction chamber. The material can consist essentially of one or more elements selected from Group VIII of the periodic table, or can consist of one or more elements selected from Group VIII of the period table.

One method of forming the material within a reaction chamber is to place a mass comprising one or more elements selected from Group VIII of the periodic table within the reaction chamber. Such mass can be in the form of a liner which is fabricated outside of the reactor and subsequently placed within the reaction chamber. Alternatively, the mask can be in the form of a material which is subjected to etching within the chamber. Such etching can cause compositions comprising one or more Group VIII elements to be expelled from the mass and deposited as a second mass along an interior of the reaction chamber.

After the material comprising the one or more Group VIII elements is provided within the reaction chamber, a silicon-oxide-containing composition is etched within the chamber. Suitable silicon-oxide-containing compositions include, for example, silicon dioxide and BPSG. In particular embodiments, the etched composition can consist essentially of silicon dioxide, or can consist of silicon dioxide.

Although the invention is described above with reference to forming a material comprising one or more Group VIII elements within a reaction chamber prior to etching a silicon-oxide-containing composition within the reaction chamber, it is to be understood that the Group VIII element can also be provided during the etching of the silicon-oxide-containing component. For instance, if a semiconductor wafer comprises both silicon dioxide and a Group VIII material thereon during etching of the silicon-oxide-containing material, the Group VIII element will be provided within the chamber at the same time that the silicon-oxide-containing composition is provided within the chamber.

It has been experimentally determined that the inclusion of one or more Group VIII elements within a reaction chamber can increase selectivity of a plasma etch for a silicon-oxide-composition relative to an organic material. For instance, if ruthenium is provided within a reaction chamber during a plasma etch of silicon dioxide, a selectivity of an etch for silicon dioxide relative to a photoresist can be enhanced. For purposes of interpreting this disclosure and the claims that follow, the term “selective” refers to an etch which is faster with respect to one material than to another, and enhancement of selectivity indicates that the difference in the relative etch rates is increased. A particular experiment is described below as Example 1.

There are several mechanisms by which enhancement of selectivity for a silicon-oxide-containing material relative to an organic material can be enhanced. One mechanism is that reactive species such as mono-atomic oxygen and mono-atomic fluorine are removed. For instance, the Group VIII elements provided within the reaction chamber can catalyze recombination of mono-atomic oxygen (which can be formed in a reaction chamber during an etch of a silicon-oxide-comprising material) with other materials to reduce a concentration of mono-atomic oxygen within a reaction chamber. As mono-atomic oxygen is highly reactive, and accordingly relatively non-selective for silicon-oxide-comprising materials to organic materials, increased selectivity can be achieved by reducing the mono-atomic oxygen concentration. If two mono-atomic oxygen species are recombined together, the result is diatomic oxygen (O₂) Alternatively, mono-atomic oxygen can be recombined with components other than monoatomic oxygen within a reaction chamber.

Another species which is highly reactive in reaction chambers is mono-atomic fluorine. The Group VIII elements can catalyze recombination of mono-atomic fluorine with other species to reduce a concentration of mono-atomic fluorine within a reaction chamber. If two mono-atomic fluorines are combined together, the result is diatomic fluorine (F₂). Alternatively, mono-atomic fluorine can be combined with carbon-containing materials to form HCF₃, CF₄, etc.

Another mechanism by which enhancement of selectivity for a silicon-oxide-containing material relative to an organic material can be enhanced with Group VIII elements is that the elements may modify organic materials to decrease an etch rate of the organic materials.

FIG. 5 shows a flow chart diagram of a particular embodiment of the present invention wherein a liner is provided within a reaction chamber. Specifically, the first step of FIG. 5 is to provide a liner which comprises tungsten, platinum, titanium and/or one or more elements from Group VIII of the periodic table within a reaction chamber. Such liner will be formed outside of the reaction chamber, and subsequently inserted within the reaction chamber. The metallic components of the liner can increase selectivity of a plasma etch for silicon-oxide-containing components relative to organic materials. For instance, it has been experimentally determined that tungsten can increase such selectivity. Particular experimental conditions are described with reference to Example 2 below.

Step 210 of FIG. 5 indicates that a silicon-oxide-containing material (specifically silicon dioxide) is etched within the reaction chamber after the liner is inserted.

FIG. 6 illustrates an exemplary apparatus 300 which can be utilized in the process of FIG. 5. Specifically, apparatus 300 comprises a reaction chamber 310 having sidewalls 312. Reaction chamber 310 also has an orifice 314 extending into the chamber and an orifice 316 extending out of the chamber. A source of plasma gases 318 is provided outside of chamber 310, and gases are flowed from source 318 into chamber 310. Source 318 can comprise, for example, one or more of CF₄, CHF₃, H₂ and C₂F₆. Although only a single source 318 is shown, it is to be understood that multiple sources can be provided, and multiple gases flowed into chamber 310. Outlet 316 is coupled with a pump 320 which removes gases from chamber 310 to maintain a flow of gases through chamber 310, and also to maintain a desired pressure within chamber 310. A substrate 322 is shown provided within chamber 310. Substrate 322 can be retained within substrate 310 on a substrate holder (not shown). Substrate 322 is shown coupled to a bias.

Also shown within chamber 310 is a focusing ring 324. Focusing ring 324 is utilized to focus reactive components from a plasma (not shown) which would be formed within chamber 310 for etching a silicon-oxide-material (not shown) associated with substrate 322. The chamber 310 described thus far can comprise conventional materials, and a conventional construction. Accordingly, sidewalls 312 can comprise, for example, quartz or ceramic materials (such as, for example, alumina).

Apparatus 300 differs from conventional apparatuses, however, in that one or more liners 330 are provided within reaction chamber 310. Reaction chamber 310 can comprise a circular construction, and accordingly, liner 330 can comprise a cylindrical shape configured to slip within chamber 310 and along sidewalls 312. Alternatively, liner 330 could comprise other shapes, and can be provided within other interior regions of chamber 310 than along sidewalls 312. Liner 330 is preferably formed of one or more of Ru, Fe, Co, Ni, Rh, Pd, Os, W, Ir, Pt, and Ti. Accordingly, liner 330 can enhance selectivity of an etch for a silicon-oxide-containing composition relative to organic materials. Exemplary compositions of liner 330 are elemental forms of one or more of the Group VIII elements, tungsten, platinum and titanium; or alloy forms of one or more of the Group VIII elements and/or one or more of tungsten, platinum and titanium.

Liner 330 can also consist of, or consist essentially of, one or more of the Group VIII elements and/or one or more of tungsten, platinum and titanium.

It is noted that a liner is different than merely being a coating on a sidewall of a reactor. Specifically, a “liner” is defined hereby to comprise a material which is formed outside of a reaction chamber, and subsequently inserted within a reaction chamber, and accordingly does not encompass deposits formed during etching of materials within the reaction chamber.

EXAMPLE 1

A first wafer comprising ruthenium in the form of ruthenium metal or ruthenium oxide is provided within a reaction chamber, and etched to form a ruthenium deposit along an interior of the chamber. Subsequently, a wafer comprising silicon dioxide and an organic photoresist material (specifically, the photoresist can be, for example, deep UV or I-line photoresist) is provided within the chamber. The silicon dioxide is etched utilizing a plasma etch comprising CF₄, CHF₃ and argon. It is found that the selectivity of the etch for silicon dioxide is enhanced relative to a selectivity which would exist in the absence of the ruthenium deposit. Specifically, it is found that the selectivity for silicon dioxide relative to the photoresist is 3.5:1 in the presence of the ruthenium deposit, whereas a selectivity of silicon dioxide relative to photoresist is measured to be 3:1 in the absence of the ruthenium deposit.

EXAMPLE 2

A liner comprising tungsten in the form of tungsten metal is provided within a reaction chamber. Subsequently, a wafer comprising silicon dioxide and an organic photoresist material is provided within the chamber. The silicon dioxide is etched utilizing a plasma etch comprising CF₄ and CHF₃.

In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents. 

1. A method of etching a silicon-oxide-containing composition, comprising: providing a liner comprising one or more of Pd, W, Os, and Ir on an interior region of a reaction chamber; providing a substrate within the reaction chamber, the substrate having a silicon-oxide-containing composition thereover; and plasma etching the silicon-oxide-containing composition within the reaction chamber, the plasma etching forming mono-atomic oxygen, the material of the liner on the interior region of the chamber increasing a rate of recombination of the mono-atomic oxygen relative to a rate which would occur in the absence of the liner in the chamber.
 2. The method of claim 1 wherein the liner comprises Os.
 3. The method of claim 1 wherein the liner comprises Ir.
 4. The method of claim 1 wherein the liner comprises W.
 5. A method of etching a silicon-oxide-containing composition, comprising: providing a liner comprising one or more of Pd, W, Os, and Ir on an interior region of a reaction chamber; providing a substrate within the reaction chamber, the substrate having a silicon-oxide-containing composition thereover; plasma etching the silicon-oxide-containing composition within the reaction chamber, the plasma etching forming mono-atomic oxygen; and recombining the mono-atomic oxygen, wherein the recombining is proximate the material of the liner on the interior region of the reaction chamber.
 6. The method of claim 5 wherein the liner comprises Os.
 7. The method of claim 5 wherein the liner comprises Ir.
 8. The method of claim 5 wherein the liner comprises W.
 9. The method of claim 1 wherein the liner comprises Pd.
 10. The method of claim 5 wherein the liner comprises Pd. 